This invention relates to rotary material processing devices in which material to be processed is set in motion by a rotary element and is so guided as to form a plurality of streams that are directed toward each other so as to collide and cause the material in the streams to intermingle and interact to process the material. A typical example of this type of device is disclosed in U.S. Pat. No. 3,531,092. The processing device disclosed in Pat. No. 3,531,092 includes a fixed hollow mixing bowl which has a rotary impeller with spiral vanes in the interior of its lower shell portion and has a set of guide vanes in the interior of its upper shell portion. At the end of a predetermined processing interval, the rotary impeller must be slowed down and a discharge opening in a side of the lower shell portion opened to allow discharge of the processed material.
The above-described processing device performs its intended function, but it has several serious shortcomings. One major problem involves the seal and bearing for the impeller. The material to be processed often includes hard granular particles, e.g. the sand in concrete mix, and these particles work their way into the impeller seal and bearing and cause them to fail prematurely. In their original state, the sand particles may in some instances be too large to penetrate the impeller seal, but they are reduced in size by collision with other sand particles in the colliding streams until they are small enough to penetrate the seal and bearing and cause them to fail.
Another problem is that it is necessary to slow the rotary impeller down to permit discharge of the processed material, which discharge takes a relatively long time.
A further problem is that foreign material such as scrap iron in the material being processed may jam or break the rotary impeller.